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APM TMB 8" F/9 Achromat


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The TMB 8” F/9 refractor taken at a dark site in Pa. That is me at the mount, my wife, and Paul Bailey looking on.


For about a year or so I first saw pictures of the large achromats on the APM website. The 7” F/6, an 8” F/6, and the 8” F/9.

At the time, I just purchased a Meade 6” F/8 LXD-75. This particular instrument had very good optics and gave terrific views.

I will admit in my 38 years of observing 95% has been deep space observing, so much of my time using the 6” refractor was DSO’s. Though I would still get some views of Jupiter and Saturn mainly after my night was almost done. I will have to say this scope though with a bit of color, gave well defined views of both planets. Even pumping the power to 400x+ on Saturn worked well.

Now some may ask why would someone who owns a 12.5” and 22” Dobs consider a refractor for deep sky observing? Well there are two main answers to that. First, the refractor gives each object a different look, with its razor sharp images and the highest contrast. Contrast is as essential to DSO observing as it is to observing planets. No they don’t have the overwhelming deep views of say my 22” Dob, but they do have a somewhat prettier view. Basically a good refractor is the Hi-Def of the telescope world.

Second reason for owning a large refractor? There is always that athlete in me that just loves challenges. I want to see how far I can push a large refractor.

Though I only had the Meade 6” Achro for about 5 months, it performed well seeing galaxies at 13 mag., as well as seeing detail in lots of familiar objects. The views were always consistently crisp and beautiful. It was these types of views from the Meade 6” that spurred me on to go after the TMB 8”.

The Scope:

Now I had a choice to make, Achro or Apo? Well my wife kind of made the choice for me. She said if you want the Apo, then I would had to sell the 22” Dob. I said “No way Jose”. So the Achro was going to be it. Now I had to decide either the 8” F/6 or F/9?

Something I had to consider was the mount. So the 8” f/6 seemed to be better for mounting purposes. But for almost all objects the F/9 was better. After lots of thought, I would gamble and get the TMB 8” F/9. Markus Ludes of APM agreed with the type of observing I do, the F/9 would be better. For the mount I decided on is the Celestron CGE. The dove-tail mounting plate is 17”.

The scope came in for the Northeast Astronomical Forum (NEAF). When I first saw it, I thought it was bigger then I imagined. Cool!

The tube is beautifully made. The retractable dew shield is nice for transporting purposes. A Moonlite focuser is finely machined, and is very smooth. It is very easy to focus on any object to the max. Optics (Russian) are fully multi-coated, with just pristine glass. No sign of scratches or any dust or dirt anywhere on the lens (outside or inside). The tube is very well baffled, and is like looking down a large dark drain pipe even in daylight. The cell is also adjustable, just incase of the need for collimation.

My choice of putting tube assembly on the CGE mount made for a wonderful match. Damping time even with the legs fully extended is about 3 seconds.

First official light:


The site I would take it to for first light is the darkest of our (Chesmont Astronomical Society) four overnight sites. This particular night was very good (though not quite the best) with a limiting magnitude of 6.5

The company I had that night were club members Dr. Robert Werkman (Doc) with his Meade 8” LX90, and 18” Obsession, and Paul Bailey and his 20” Obsession. Unfortunately no other members could make it this particular Tuesday night.

Having both the 8” SCT and the two very large Dobs provided a great way to compare views, and see how good the big refractor is. Also my vast number of objects viewed from my 15+ scopes I own (and owned) over the years would also help in the review of the scope.

After setting up the mount with the legs fully extended, it was time to put on the tube. Now the tube assembly weighs in around 45 pounds. Not real heavy for me, but it is bulky. The mounting rings and plate are almost 6 feet high. My solution for safely putting on the tube assembly brought me back to my old powerlifting days. My wife put together two lifting straps with Velcro on the ends. So I simply put the straps around the tube, spaced about shoulder width apart, and balanced for the lense end of the tube. I basically cleaned (but no jerk) the tube up on the mount. Easy, and no worry about dropping it.

Once I had the mount aligned, we just waited for the “real dark” to set in. Though you get tired of bundling up for cold observing here in the north during Winter. At least it doesn’t take until almost 10:30pm for it to get dark like this time of the year.

Optical Quality:

My familiarity with optical quality reflectors is more than high quality refractors. So my star test with this instrument is NA, though what I could tell seemed very good with no immediate determined problems. I can say with the following information on my observing night will validate the excellence of these optics. Basically that is how all scopes are really judged.

Observing the objects: Night 1

Planets

First, let’s get right to it. As mentioned before, I am first and foremost a DSO observer. Still I wanted to know how well it does on planets. So by the time the optics settled, Saturn was way too low in the sky. Jupiter was the target then.

The seeing at this time (early) was just okay. So I first inserted a Meade 5k 14mm Plossl (129x). This gave a nice view of the planet. Now how much color did this Achro show? Not too much, less than my Meade 6” did. Well let’s keep going. Next came the 7mm Nagler (257x). Lots of detail on the disc. The focus was clear with some seeing issues (not the scopes fault). So I said lets just go for it a bit and push the limit a little. I went to 400x+. Well, as the mount kept tracking the planet. Seeing would pop for a moment or two. Jupiter was great. Lots of detail within the belts. WOW! Hey, this is coming from a DSO observer, so you know it was good if I was excited!

Ok, let’s get to the good stuff. DEEP SKY

Leo

Now what will be official first light object? Well, how about the Leo Trio (M-65, M-66, and Ngc-3628).

So I entered M-65 in the hand controller, and the big guy swung right over to the Trio.

I looked into the Meade 5k 32mm Plossl (56x), and was greeted by one excellent view. All three galaxies bright and clear, almost poster like!

I put in a Meade 5k 18mm UWA (100x). Though all three were still in the field of view, I slewed the scope just onto M-65 and M-66. Even at this relatively low power detail was very much evident. M-65 was long with a bulging center. M-66 showed the elongated bar in the center with hints of spiral arms. Slewing to the third galaxy Ngc-3628 I found it was bright with that dark lane very apparent cutting through the galaxy. I was pleasantly surprised how much detail was evident at this power. Switching to an 11mm Nagler (164x) showed M-65 big and bold with a slight hint of the dark lane. M-66 at this power definitely showed spiral arms, and Ngc-3628 was reaching almost end to end in the eyepiece field.

Now that was first light! Both Doc and Paul took their time analyzing each view. Both just said “WOW”!

On to the Ngc-3190 group (Hickson 44) I put in the 18mm UWA (100x) for the first look. Ngc-3193 was a nice bright pearl-like object. Ngc-3190 is showing that nice edge-on appearance with a bright core. Ngc-3185 showed pretty much a round disc with a stellar nucleus. Now switching to a 10mm Radian (180x) gave me a surprise with seeing the 4th member Ngc-3187 a low surface brightness 13.5 mag barred spiral. Previously the smallest scope (from another site) in which I saw this galaxy was with my 12.5” Dob.

Next were the interacting galaxies Ngc-3226/3227. At 100x each galaxy showed its shape and bright cores. Ngc-3226 a round elliptical, and Ngc-3227 a bit of an elongated spiral. Ngc-3222 was seen just west of the pair. Nice view.

Ursa Major

Though there are many galaxies to see in this constellation, earlier in the evening I suggested the Ngc-3995 group (Arp 313) for the big Dobs. So Paul with his 20” gave this group one spectacular view. Doc also had them in his sights in his 18”. Both big Dobs provided a stellar view! So of course I punched in the numbers, and the refractor slewed to the group. Now in both big Dobs the galaxies (Ngc-3991/94/95) gave a photographic view. In the 8” refractor all three were very apparent. Ngc -3994 showed a stellar nucleus. Ngc-3995 is largest but with a lower surface brightness, still showed well. Ngc-3991 is the most interesting. That has a slightly elongated bulge that seems to have a thin tail heading SW. In fact there is a dark gap between this bulge and tail that was very apparent in the 20” and the 18”. This gap was also seen in the 8” refractor with a 7mm type 6 Nagler (257x). This is an interacting system.

My thought at this time was this big refractor is really bringing in the views. Both Doc and Paul conveyed to me that this scope is quite a machine. From this point on there is lots of optimism, and the Universe is mine. Well, for this one special “first light” night.

Canes Venatici


One of my favorite pair of galaxies in Canes Venatici is Ngc-4485/4490. Slewing the scope to their position using the 32mm 5k plossl (56x) immediately gave on fine wide field view. The large spiral Ngc -4490 has that teardrop shape, with the western arm pointing to its companion Ngc-4485 an irregular galaxy. Inserting a Meade 4k 14mm UWA (129x) which gave a splendid view of both field and detail. Ngc-4490 is easily showing a bright core with the western arm hooking towards Ngc-4485.

Next was the bright irregular Ngc-4449 with the 32mm (56x) the galaxy showed that rectangle look also to the NE was the edge-on galaxy Ngc-4460 pointing towards a double star. Really a nice field. Centering Ngc-4449, I inserted the 10mm Radian (180x).

The galaxy showed a stellar nucleus, with some bright lumps or knots here and there, particularly the bright HII region on the north side. I’m seeing detail that my 12.5” Dob usually sees. Paul’s view in the 20” is stunning though much of the detail was also seen in the 8” refractor.

On to M-106. With the Meade 18mm 5k UWA (100x) the galaxy was already big and bold. Showing a very bright nucleus, and a large patchy halo. Ngc-4248 a small 12.5mag elongated galaxy to the NW was easily seen. A Meade 5k 8.8mm UWA (204x) showed a bit more detail with a glimpse of the arms. Also Ngc-4248 showed a bright elongated central region with a delicate outer region, and faint star on its western edge.

M-51 was next. At 100x the galaxy and field was real nice. So I inserted the 11mm Nagler (164x) and the spiral arms were quite visible. The bridge I would like to go for on a better night. With averted vision it seemed to be there. Contrast is really helping here.

Now came to one of my favorites in Canes Venatici, Ngc-4631 with its companion Ngc-4627, and the nearby galaxy Ngc4656. Using the 32mm 5k Plossl (56x) gave one heck of a view of these galaxies. Here again poster like! At this time Doc’s 18” was centered on Ngc-4631. If you have never seen this galaxy, it is a must next clear dark night. This is one of the secret gems of the night sky.

The 18” view was showing photographic detail, as well as its small companion Ngc-4627. Much of the detail that was seen in the 18” Dob, as we looked through both scopes, was also apparent in the 8” refractor as described below.

I inserted the 11mm Nagler (164x) in the big refractor. WOW! The galaxy was big and bold with star clouds. Ngc-4627 also showed some brightning in the core area. Slewing to the third galaxy Ngc-4656 was also quite a sight. The curve NE of center was very apparent. Also the very low surface brightness area to the SW was also seen, contrast again making this view possible.

Coma Berenices

First up was the galaxy Ngc-4559 that seems to lose out in the constellation with other galaxies like Ngc-4725, M-64, and of course Ngc-4565.

At 56x the galaxy showed a large oval shape, brighter towards the center, with a couple of faint stars on the SE side. Putting in the 11mm Nagler (164x) it started to show some nice detail. The core area is elongated, surrounded by a faint halo. Throughout the halo are some patchy areas, particularly SE of the core.

Now on to my favorite object in Coma, and my favorite object to view in my 22” Dob. Ngc-4565 the “Great Edge-On”. With an 18mm UWA (100x) the galaxy and surrounding view was beautiful. Switching to the 11mm Nagler (164x) the galaxy was sporting its dark lane, and the star-like nucleus within the central bulge. Also the 13.5 mag. elongated galaxy Ngc-4562 was visible to the west.

Not quite the view of my 22” Dob, but I’ll take it. This 8” refractor is a bit of a galaxy machine. Much more than what I had expected. Clarity and contrast, as well as decent light gathering can go far.

Draco

This is really a fine constellation for galaxy hunters, particularly when the other galaxy constellations are far beyond meridian. Ngc-5907 is a splendid edge-on galaxy. At 56x the galaxy was a long thin sliver slightly broader in the center region. Moving up to 164x the galaxy extended from one side of the field to the other. With averted vision a hint of the dark lane was visible.

Moving NE is the Draco Trio, containing Ngc-5981/5982/5985. At 100x gave a nice view showing Ngc-5985 (the largest) and a nice tilted spiral, Ngc-5982 (the brightest) a slightly oblong elliptical and Ngc-5981 (the faintest) is a 13th mag. edge-on spiral.

Putting in the 11mm Nagler showed a tight core in Ngc-5985, surrounded by a mottled halo. Ngc-5982 was well concentrated with a bright stellar nucleus. Ngc-5981 actually stood out very well, fairly long and thin with a slight brightening in the core area.

Virgo

Basically I had the scope go to the M-84/86 area and did a 25 to 30 minute Virgo tour with the 18mm UWA (100x). WOW! Galaxy upon galaxy were everywhere against the velvety black sky!

Observing the Virgo cluster with the TMB 8” refractor was something I was looking forward to. I will of course do the tour again next Spring, and maybe make it a most of the night tour.

Serpens Caput

The views of Globular clusters through large refractors are amazing, of course M-5 is no exception. With the 14mm UWA (129x) the view was stunning to say the least! With a multitude of pinpoint stars radiating from a blazing core in a canvas of black sky, M-5 looked 3-D!

So I went up a little in power to 400x+. Now I was inside M-5! The stars even at this power were pinpoint, with the core area highly resolved.

Hercules

M-13 was my final target of the night. With the Meade 32mm 5k plossl (56x), the view with the cluster and its far away background companion the galaxy Ngc-6207 was terrific. I could stare at this image for awhile. With the 11mm Nagler (164x). Ngc -6207 had an oblong shape to it with a bright stellar nucleus.

The view of M-13 was the best I’ve seen in a scope under 12.5”. The over all quality of the image was the best I’ve seen. A huge ball of stars focused to a point in a pitch black sky, here again 3-D like!

End of night 1 with the TMB 8” F/9 refractor. SUCCESS!

Night 2


Unfortunately this night at the same observing site was not up to par. More humidity then predicted knock down the transparency. So I will only report of two objects, though both are very well known.

M-27 the Dumbbell nebula

At 56x, the nebula with that marvelous star field was stunning. I could not pull my eye from the 32mm plossl. The nebula and star field was absolutely crystal clear with such contrast, that the nebula looked like it was floating in the field. 3-D again!

Inserting the 11mm Nagler (164x) with no filter, the nebula showed its hour glass appearance, but the outer parts (E & W sides) of the nebula actually made it more of a globe appearance. A few stars are seen throughout the nebula including the 13.9 mag central star.

M-57 the Ring Nebula


Back in 1971 I saw this object clearly for the first time in my 6” Newt. That view gave me the start of being a DSO observer. Now 35 years later this wonderful object was in my new 8” refractor. Here again at 56x the nebula looked like it was floating in another marvelous star field.

Pumping up the power with an 8.8mm UWA (204x) the nebular showed very well. I pushed the power a bit more to 400x+. WOW! Subtle shadings of brightness on the Ring gave a textured look.

Comparing views on this night with my old Meade 16” Dob now owned by club member Chris Fessett. The 8” f/9 refractor gave the larger Dob a run for the money on this object.

In fact Chris thought the view through the refractor were more appealing, thanks to the superior contrast and clarity. Both scopes were at 400x+.

Central star? Not this time on this night. The 14.7 and 14.9 mag stars on the northern side were visible, but not easy in this sub-par night. Next time on a better night? Hey you never know.

Summary

This is a remarkable time for us as amateur astronomers. Looking back to 1968 remembering how I got started on this incredible journey. Now for me 38 years later owning a 22” Dob and a 8“ refractor, it’s really amazing! Now both my 12.5” Dob and 4.7” refractor are now my grab-an–go scopes.

My thought on the TMB 8” f/9 Achro is that it’s a terrific scope. Though for some this could be a bit much to handle. It really is a BIG scope. Bigger in person then the picture. Mounts smaller than the Celeston CGE, may have a tough time, and for observing only it may work, but not recommended.

As stated in the article, the optics are very good. Contrast and clarity, with the ability to handle high power is its strengths. Also it is 8” of unobstructive optics, so it does gather a pretty decent amount of light.

Yes, being an Achromat, some color is there, though not intrusive. Many of the filters that are out there will work well for this scope. Jupiter with no filter, great detail was still visible. Very good optics is the reason.

For deep space (my thing) it’s terrific. Every bit what a big refractor can do both Achro and Apo.

Why do refractors do so well on deep space objects? The reason is the refractor provides some essential ingredients to the deep sky observing pot. Contrast and clarity are two key ingredients. Also good refractors can handle lots of power. This is another ingredient that allows detail to be seen.

With great contrast, clarity and the ability to handle high power, the eye is able to perceive detail more easily. Inch for inch a refractor is second to none, and can perform as well as other types of scopes that are slightly larger. It’s not always just total light gathering, but how well the light is transmitted to the eye.

How did the TMB 8” F/9 compare to the 16”, 18” and 20” Dobs? Actually, very well. Most objects seen in the Dobs were visible in the 8" refractor and much of the detail as well. The Meade 8” SCT (a nice scope) images were not as bright, clear, or detailed as the refractor. This is not a knock on the SCT, but more on the ability of a large refractor.

Galaxies near 14th magnitude were seen in the refractor, and I’m sure on even a better night galaxies near 15th magnitude is possible, especially those with a high surface brightness. We will find out in up coming observing nights.

As you can tell refractors are not planetary scopes only. They make wonderful deep sky scopes providing beautiful views. Many owners of good refractors both Apo and Achro would agree, particularly 4” or larger refractors.

Now in most cases the BIG Dobs rule the deep sky observing world, but large refractors do have a place as you can see from just two nights of observing. So the TMB 8” f/9 refractor compliments my 22” Telekit Dob (Swayze optics), and not competes with it.

So for now (and per the wife) ends my telescope buying. My dream of owning both a giant Dob and a giant refractor has come true. Now I can’t wait for the next clear moonless night.

So many galaxies, so little time or clear moonless nights!

PROS

Great optics with great contrast and razor sharp images.
Beautifully made
Nice focuser
APM’s Markus Ludes answered all my questions (lots of them) via e-mail.
It’s BIG

CONS


Needs a good beefy mount
Little color
It’s BIG


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